1. Field of the Art
The present invention relates to an automatic blood-pressure measuring apparatus capable of automatically measuring blood pressure of a living subject such as a human body.
2. Description of the Prior Art
An automatic blood-pressure measuring apparatus is known, which comprises a cuff or occluding device for applying a pressure force to a body member of a living subject such as an arm or foot of a human or animal body, and blood-pressure determining means for determining blood pressure levels according to a variation in a blood pulse wave generated in relation to a change in the pressure force applied by the cuff device, for example, according to: presence or absence of Korotkoff sounds (blood sound waves) which are detected as sounds due to a blood flow through an arterial vessel of the subject; a variation in amplitude of cuff pressure pulsations generated in synchronism with beats of a heart of the subject; a variation in magnitude of pulsating movements of a wall of an arterial vessel of the subject which are detected by means of an ultrasonic wave. In the case where such an automatic blood-pressure measuring apparatus is used to monitor the subject (patient) for a comparatively long period of time in a continuous manner during or after a surgical operation of the subject, it is a common practice to repeat a blood-pressure measurement cycle periodically in response to an actuation signal which is generated at a predetermined time interval to actuate the measuring apparatus to execute a series of blood-pressure measuring steps.
In such a known type of automatic blood-pressure measuring apparatus wherein the blood pressure of the subject is measured periodically, there is recognized an inconvenience that a blood pressure measurement cycle does not always take place while there exists an abnormality or disorder associated with a blood circulatory system (circulatory organs) of the patient, for example: abnormal decrease in blood flow volume (blood insufficiency) at a certain point of the system, abnormal or irregular interval of heart beats, and abnormal number of the heart beats per unit time. In other words, the known arrangement fails to achieve the measurement at medically suitable timings at which the conditions of the subject can be well grasped. Stated the other way, to exactly grasp the conditions of the subject during or after a surgical operation thereof, it is medically preferred to know the blood pressure levels of the subject or patient during a time period while the subject is suffering from some functional trouble with the blood circulatory system.
In the meantime, it has been considered or proposed to shorten a time interval at which the actuation signals indicated above are generated, in order to activate the measuring apparatus more frequently, so that some of the measurement cycles are effected at timings closer to the period of abnormality in the blood circulatory system of the subject. In this instance, however, the body member is accordingly frequently occluded by the cuff, and the consequent frequent application of a cuff pressure to the body member will discomfort the patient.